Application error does not raise alert

Hi SDN Warriors

A question regarding the alerting! We set up a simple alert category to be informed by mail for any kind of error. Everything works fine, we have been informed by mail if we receive a system error or what ever.

Only one interface is not raising this alert. The synchronous interface raises sometimes an exception of kind

<SAP:Category>Application</SAP:Category>

<SAP:Code area="UNKNOWN">APPLICATION_ERROR</SAP:Code>

But we do not receive an alert.

Is this not an error from alerting point of view or is it maybe a bug. We are on PI70 SPS13.